feat(observe): record real tool failures from PostToolUseFailure

Claude Code sends failed tool calls to the PostToolUseFailure event.
ADAM registered only PostToolUse, so it never saw a real failure, and
every tool_error_loop came from ERROR_RE matching successful output.

Handle PostToolUseFailure in adam-observe.mjs through the PostToolUse
detectors. Shape the error string as an is_error response. An interrupt
is an abort, so it counts as a tool event but gets no fingerprint.
Register the event in settings.json.example.

Tests 9b and 9c added: 150 passed, 0 failed.

Claude-Session: https://claude.ai/code/session_014prTNuJnKuwcAd28vUZAnN

settings.json.example

@@ -34,6 +34,17 @@
         ]
       }
     ],
+    "PostToolUseFailure": [
+      {
+        "matcher": "",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "node \"$HOME/.claude/hooks/adam-observe.mjs\""
+          }
+        ]
+      }
+    ],
     "SessionStart": [
       {
         "hooks": [